Seroepidemiology of malaria in Karnataka State: longitudinal study of a population from an area with high incidence at Kolar, South India.

Serologic methods have considerable value in epidemiologic surveillance of malaria. Antigens prepared from P falciparum cultured in vitro have been found to be sensitive and to a certain extent specific in the IFA test to detect malarial antibodies in the sera from a population continuously exposed to P falciparum and Plasmodium vivax infections [1]. However, it is necessary to assess the serologic data against the results of conventional examination of peripheral blood smears in monitoring the effect of antimalaria measures on malaria transmission. With this objective, we studied a randomly selected population from GPHU, which is located in an area in the Kolar District of the state of Karnataka where malaria is known to be endemic. During the transmission period of 1980 (from July to November), the annual parasitic incidence was 202 per 1,000, with 78% due to P vivax and 22% to P falciparum. The antimalaria measures were subsequently intensified by the GPHU staff, which lead to a decrease in the incidence of malaria in 1981 (60 per 1,000, with 91% due to P vivax and 9% to P falciparum; data obtained from GPHU records). Serum samples were collected after each transmission period and tested by IFA using a local isolate of P falciparum as antigen. There was a marked decrease in the number of seropositive samples in the second batch among children less than 10 years of age and a threefold decrease in malarial antibody titers up to the age of 15 years.(ABSTRACT TRUNCATED AT 250 WORDS)